Common problems guide

The most common Ariston E-System ONE problems

The faults most likely to send a Ariston E-System ONE into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

46 documented codes
6 most common
0 DIY-safe checks
6 engineer needed

The 6 most common faults

01
3 05 High Engineer

Your boiler's internal computer is experiencing a communication error, which means it cannot operate safely and has shut down.

Est. cost
£250-450
Parts
Main PCB, Wiring harness
Full guide for 3 05
02
3 06 High Engineer

Your boiler's internal computer is experiencing a communication error and has shut down to prevent potential system damage.

Est. cost
£250-450
Parts
Main Printed Circuit Board (PCB)
Full guide for 3 06
03
6 10 High Engineer

Your boiler has detected that it is running much hotter than it should be and has shut itself down to prevent damage.

Est. cost
£120-250
Parts
NTC Temperature Sensor, Primary Heat Exchanger, Central Heating Pump
Full guide for 6 10
04
7 11 Medium Engineer

Your boiler is struggling to accurately read the temperature of the water returning from your heating system, which is preventing it from running your heating correctly.

Est. cost
£120-220
Parts
Return NTC sensor, Wiring harness
Full guide for 7 11
05
7 12 Medium Engineer

Your boiler is having trouble reading the temperature in one of the secondary heating zones, which may prevent that part of your home from heating up properly.

Est. cost
£120-200
Parts
NTC Temperature Sensor, Wiring harness
Full guide for 7 12
06
7 13 Medium Engineer

Your boiler is having trouble communicating with one of the temperature sensors for your heating system, which may cause your heating or hot water to work inconsistently or stop altogether.

Est. cost
£120-220
Parts
NTC Temperature Sensor, Wiring harness
Full guide for 7 13
Parts most often replaced

on the Ariston E-System ONE

Main PCBWiring harnessMain Printed Circuit Board (PCB)NTC Temperature SensorPrimary Heat ExchangerCentral Heating Pump

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Ariston shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
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See the full 46-code list for the Ariston E-System ONE

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →